Abstract

Background

Non-adherence to adjuvant endocrine treatment (ET) among breast cancer patients has been associated with worse prognosis. We sought to identify factors affecting non-adherence to ET, taking into account determinants at baseline and follow-up.

Methods

From linkage between Swedish national registers, we identified all women diagnosed with stage I-III, ER-positive breast cancer in Stockholm-Gotland, Uppsala-Örebro and Northern Sweden between 2006 and 2009. A total of 4,413 women who had at least one dispensation of tamoxifen or aromatase inhibitors (AIs) and 5 years of follow-up were included in the analysis. A medical possession ratio (MPR) of

Results

During follow-up, 1,131 (25.6%) women became non-adherents. The following determinants of non-adherence were identified: age, marital status, region of diagnosis, private hospital, tumour size, lymph node metastasis, tumour grade, HER2 status, type of surgery, adjuvant chemotherapy, type of ET, pre-diagnostic hormone replacement therapy, the use of symptom-relieving drugs at baseline and during follow-up, baseline scores and any increase in Charlson co-morbidity index (CCI). In multivariable analysis, non-adherence was only associated with younger age (OR: 0.67; 95%CI: 0.50-0.90 and 0.66; 0.48-0.92 for age 50-65 and 65+ compared to

Conclusions

Our study identifies socioeconomic subgroups with increased risk of non-adherence that may be of use when measures for improving adherence are tested. Women with pre-diagnostic use of HRT may represent a biological subset with a disposition for side effects from ET.